1. Field of the Invention
This invention relates generally to methods and mechanisms for clock timing in a network timing.
2. Description of Related Art
Synchronous optical networking (SONET), is a method for communicating digital information using lasers or light-emitting diodes (LEDs) over optical fiber. SONET technology was developed to replace the Plesiochronous Digital Hierarchy (PDH) system for transporting large amounts of telephone and data traffic and to allow for interoperability between equipment from different vendors. SONET is widely used today in the U.S. and Canada.
Time-Division Multiplexing (TDM) is a type of (typically) digital multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but physically are taking turns on the channel. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. One TDM frame consists of one timeslot per sub-channel. After the last sub-channel the cycle starts all over again with a new frame, starting with the second sample, byte or data block from the first sub-channel. TDM is used in the differential method of SONET clocking.
SONET differs from PDH in that the exact rates that are used to transport the data are tightly synchronized across the entire network, made possible by atomic clocks. This synchronization system allows entire inter-country networks to operate synchronously, greatly reducing the amount of buffering required between elements in the network. Thus, any improvement in the mechanisms and methods for clock synchronization in a SONET system is desirable.
The foregoing objects and advantages of the invention are illustrative of those that can be achieved by the various exemplary embodiments and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other objects and advantages of the various exemplary embodiments will be apparent from the description herein or can be learned from practicing the various exemplary embodiments, both as embodied herein or as modified in view of any variation which may be apparent to those skilled in the art. Accordingly, the present invention resides in the novel methods, arrangements, combinations and improvements herein shown and described in various exemplary embodiments.